1. Technical Field
The present disclosure relates to electrosurgical forceps for assuring uniform sealing of tissue when performing electrosurgical procedures. More particularly, the present disclosure relates to open, laparoscopic, or endoscopic bipolar electrosurgical forceps that includes reactive elements for driving different amounts of current through different parts of a jaw member of the forceps in order to achieve a more controlled distribution of energy along the length of the jaw.
2. Description of the Related Art
Forceps utilize mechanical action to constrict, grasp, dissect and/or clamp tissue. Electrosurgical forceps utilize both mechanical clamping action and electrical energy to effect hemostasis by heating the tissue and blood vessels. By controlling the intensity, frequency and duration of the electrosurgical energy applied through the jaw members to the tissue, the surgeon can coagulate, cauterize and/or seal tissue.
In order to effect a proper seal with larger vessels or thick tissue, many known instruments rely on control of mechanical parameters. Two predominant mechanical parameters that should be accurately controlled are the pressure applied to the tissue and the gap distance between the electrodes. As can be appreciated, both of these parameters are affected by the thickness of vessels or tissue. More particularly, accurate application of pressure is important for several reasons: to reduce the tissue impedance to a low enough value that allows enough electrosurgical energy through the tissue; to overcome the forces of expansion during tissue heating; and to contribute to the end tissue thickness, which is an indication of a good seal.
Even with control over mechanical parameters, however, the tissue portion nearest the pivot of the opposing jaw members tend to receive more energy delivery than the portions which are distal thereto. Resistance is expressed as resistivity multiplied by, the length divided by cross-sectional area. The resistance, thus, changes as the pressure of the jaws affects the thickness of material held therebetween and the jaw surface area changes. The increased pressure at the distal ends increases both electrical contact and decreases thickness of tissue, thereby requiring, in some instances, a greater amount of energy between the distal ends of the opposing jaw members in order to properly and effectively seal larger vessels or tissue. Relying on mechanical parameters alone, without taking into account energy dissipation along the length of the jaw, can lead to an ineffective seal. Energy distribution, if properly controlled, can assure a consistent and reliable tissue seal by compensating for changes in tissue impedance caused by changes in pressure, surface area, and thickness.